OSS stands for Online Support System. OSS is a tool provided by SAP to help the customer for solving there problems. Through OSS notes sap provides update on patches and provide up to date information. A SAP Customer can login with his ID and Password to raise a ticked for there issues in SAP but this service are not extended if you have modified or extended the functionality of SAP program
OSS notes can be seen if you have access to SAP Service Marketplace link: service.sap.com. After getting into this portal if you click on “SAP Support Portal” it will ask you for login ID and password. Enter your login ID and Password to get in. you can also get into the link directly through this link https://service.sap.com/notes
OSS notes are now called SAP Notes. OSS notes are raised for different functionality. It can be raised for a bug correction or program correction and it can also be raised for implementation of updates or new functionality to SAP business process.
You can search for the already published OSS note from the above link given. To find OSS notes related to you, search by the most appropriate search term related to your problem. You can first try by putting the functional module that your use. There are obvious reasons to get plenty of OSS notes so try to filter your search criteria to get the exact notes to match your requirement.
If you are not yet able to get how to see a OSS note or to raise a OSS note then get help of the support staff of SAP.